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Transient O2-dependent effects of CO2 on ventilation in the anesthetized mouse

100%

Pokorski M., Izumizaki M., Homma I.

Journal of Physiology and Pharmacology

2005

tom 56

nr 3

In this study we sought to determine the effects of background hyperoxia on the ventilatory response to hypercapnia. We addressed this issue by examining the temporal profile of the first minute transients of minute ventilation, and its frequency and tidal components, in response to 5% and 10% CO2 each co-applied with the natural (balanced with air) and hyperoxic (balanced with O2) levels of oxygen. The study was performed on the urethane-anesthetized, tracheostomized, spontaneously breathing mouse, placed in a flow-through body plethysmograph. We identified an early suppressant effect of CO2-in-O2 on breathing frequency. The frequency declined to 88.5 ±1.4% and 87.8 ±1.9% relative to the pre-test, baseline level for 5% and 10% CO2, respectively. There was a compensatory rise in tidal volume and no major change in the overall ventilation. In contrast, CO2-in-Air resulted in ventilatory stimulation caused in equal measure by frequency and tidal components. Thus, the inhibitory effect on breathing frequency of the CO2-in-O2 resulted from the O2 content in the mixture and had the temporal characteristics consistent with carotid body function. In conclusion, transient O2-dependent effects can bear on the nascent hypercapnic ventilatory response. The complexity of the O2-CO2 interaction regarding the breathing pattern components should be taken into account while designing the optimal conditions for a hypercapnic test.

Alterations in the hypoxic ventilatory response with advancing age in awake rats

80%

Pokorski M., Antosiewicz J.

Journal of Physiology and Pharmacology

2010

tom 61

nr 2

This study seeks to determine the influence of aging on hypoxic ventilatory responsiveness. We addressed the issue by comparing the hypoxic ventilatory responses in three age-groups of conscious rats: 3, 12, and 24 months old animals. Ventilation was recorded in a whole body rodent plethysmograph. Minute ventilation (E), respiratory rate, and tidal volume were considered for analysis. The rats were subjected to two levels of acute hypoxia: 14 and 11% O2 in N2. Hypoxic exposures were separated by a 15 min recovery interval in air. The part of the study between the 12 and 24 months age interval was longitudinal in that the same animals were studied twice, whereas the youngest animals belonged to a separate breed. All data were normalized to body mass. All hypoxic responses were biphasic with the stimulatory peak at 0.5 min after onset of hypoxia. The results demonstrate that there were no appreciable differences in magnitude of the peak hypoxic E responses between 3 and 12 months old rats. The hypoxic E responses and also the hypoxic ventilatory gain were, however, enhanced in the senescent rats. In these rats, the increment in peak E from 14 to 11% hypoxia amounted to 364.1±95.8 ml.min-1.kg-1, which was more than double compared with 12 and 3 months old rats (P<0.02). We conclude that ventilatory responsiveness is not curtailed in senescent rats. The respiratory system is able to compensate for any age-related handicaps in the respiratory system to maintain a stimulatory response to ventilatory stress.

Ograniczanie wyników

2 Journal of Physiology and Pharmacology

2 Pokorski M.

1 Antosiewicz J.

1 Homma I.

1 Izumizaki M.

1 2010

1 2005

Wyniki wyszukiwania

Transient O2-dependent effects of CO2 on ventilation in the anesthetized mouse

Alterations in the hypoxic ventilatory response with advancing age in awake rats